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TI fuel gauge predicts battery life in mobile phones

Posted: 27 Sep 2007     Print Version  Bookmark and Share

Keywords:Impedance Track technology; fuel gauge IC  mobile handheld 

Texas Instruments Inc. has introduced its system-side fuel gauge integrated circuit (IC) with Impedance Track technology for smart phones and other handhelds. The 2.5 mm x 4 mm gauge predicts battery life with 99 per cent accuracy to extend run-time, protect data and provide a better user experience for mobile handheld users.

"As mobile devices add more functionality, such as high-definition video and data transmission, consumers want to operate their devices just like notebook computers and expect to know remaining battery capacity," said Dave Heacock, senior VP of TI's high-volume analogue and logic business. "Today's announcement builds on TI's innovative battery fuel gauge technology, which is used in millions of notebook computers. Our portable device customers asked to incorporate the technology into their mobile designs—and now they can."

"The bq27500 represents the next levels of technological advancement in the area of Gas Gauging using TI's Patented Impedance Track Technology. Aimed at Portable Consumer Electronics devices, BQ27500 accurately predicts battery run times. The end consumer now has more power in his hands, literally, with the added advantages of minimised data loss and optimised utilisation of existing battery energy," said Ram Ananth, Engineering Manager, Power Management Products, Texas Instruments (India) Pvt Ltd

The bq27500 accurately measures data from a device's single-cell Li-Ion battery to predict remaining battery capacity under all conditions, even as a battery ages. The tiny IC analyses precise state-of-charge by correlating between a battery's voltage and cell impedance, or resistance, and its current integration to adjust remaining state-of-charge up or down the predicted discharge curve.

Most handhelds today do not accurately gauge remaining battery capacity, but simply measure the cell voltage to guess the capacity. Traditional "coulomb counting" techniques used in some handhelds require static and unreliable modeling methods that attempt to compensate for discharge rate, temperature and age of the cell, and must also model self-discharge and other non-measurable currents. Since these models have an inherent error, which is difficult to minimise, an end-user will not accurately know how much run-time remains as the battery ages.

The bq27500 directly measures the effect of a battery's discharge rate, temperature, age and other factors to accurately predict remaining life within one per cent error. By measuring and storing real-time battery impedance values, the IC automatically adjusts to changes in full capacity as a battery ages. State-of-charge and full capacity are calculated from the voltage and impedance measurements, eliminating the need to re-learn from a charge and discharge cycle.

As handheld systems provide more functions, the need has grown for accurate fuel gauging to intelligently manage available power, alert the user of system operating-time, and extend the run-time of the system as far as possible. Accurate battery data is used by applications processors, such as TI?s OMAP3410 processor with SmartReflex power and performance technologies, to optimise the system's complete mobile power operating system. For instance, the system can leverage low-power modes, clock gating, clock throttling and dynamic voltage and frequency scaling capabilities based on battery capacity. The bq27500 provides an accurate reserve energy warning, which allows a system to save data to non-volatile memory at the end of a battery's discharge, so work is not lost when battery life runs out.

The bq27500 is implemented on the host system's board, and can support an embedded or removable battery. System-side implementation allows a handheld manufacturer to save cost by designing an end-equipment that does not need extra electronics added to the battery pack. As batteries continue to shrink in size, integration of electronics on the battery becomes more of a challenge. System-side control and manage other main battery management functions, such as battery pack authentication.

Pricing and Availability

The bq27500 is available today in volume from TI and its authorized distributors. Available in a space-saving 12-pin, 2.5 mm x 4 mm SON package, the device's suggested retail pricing is Rs.38.43 ($0.95) in 1,000-piece quantities. Evaluation modules of the bq27500, design application notes, user guides and TI?s software design tool are available through power.ti.com.

Comprehensive Battery Management Portfolio

TI provides high-performance battery power management products for any single-cell or multi-cell battery powered design, including a full range of battery fuel gauges, battery charge management, and battery protection and authentication solutions. The bq20z90 and bq20z70 multi-cell battery fuel gauges target notebook computers and portable industrial applications. TI's bq27000 family of fuel gauge ICs supports single-cell battery packs. For more information on TI's battery management products, see: www.ti.com/battman.




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